[SOLVED] Calculating required number of wins

Hi

I'm making a spreadsheet which will calculate the number of wins required to achieve a given win ratio (expressed as a percentage.) My problem is when someone wins an additional round, they have also played one extra round (and this variance causes the required number of wins to change.)

The table looks something like this:

Wins: www
Rounds Played: xxx
Win%: yy%

Required Win%: zz%
Number of Wins Required: ??

My question is - What formula would I use to calculate the number of wins required?

This is quite frustrating since I know it can be done and I'm sure I've done it before, but I can't put my finger on it.

I'm making a spreadsheet which will calculate the number of wins required to achieve a given win ratio (expressed as a percentage.) My problem is when someone wins an additional round, they have also played one extra round (and this variance causes the required number of wins to change.)

The table looks something like this:

Wins: www
Rounds Played: xxx
Win%: yy%

Required Win%: zz%
Number of Wins Required: ??

My question is - What formula would I use to calculate the number of wins required?

This is quite frustrating since I know it can be done and I'm sure I've done it before, but I can't put my finger on it.

You have:
The number of wins so far (W)
The number of games so far (G)
The percentage of wins required (R)

And you want to know how many more wins (y) it will take you to reach the winning percentage, right?

K,

100*W/G = Percentage wins so far

100*(W+y)/(G+y) = R
The y is your only unknown, and incidentally, the answer you'll be looking for...

Obviously the calculation does not factor in possible losses, but that is not necessary.

It certainly is a bizarre spreadsheet - It's for an online game which awards titles based on a given ratio for round-type wins. The spreadsheet is designed to calculate the required number of extra rounds needed in-order to achieve the set ratio.